How Much HP Is That Electric Fan Really Saving You?
10-09-2009, 08:00 PM
#1
Le Mans Master
Thread Starter
How Much HP Is That Electric Fan Really Saving You?
In this month's Car Craft Magazine they run a dyno test on a modified SBC. To check the hp gain associated with changing belt and pulley ratios, they "load" the alternator with an electric fan (and it ain't all that big). The results...
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
10-09-2009, 08:18 PM
#2
Race Director
Predictable.
Running a fan directly has no conversion losses.
Turning rotary motion into electricity and then back to rotary motion again has losses at both end. And those cheap motors are probably only about 60% efficient
I like my clutch fan, it usually spins fairly free most of the time.
Doug
Running a fan directly has no conversion losses.
Turning rotary motion into electricity and then back to rotary motion again has losses at both end. And those cheap motors are probably only about 60% efficient
I like my clutch fan, it usually spins fairly free most of the time.
Doug
10-09-2009, 08:33 PM
#3
Le Mans Master
Member Since: Nov 2000
Location: Going too fast over the hill. Iowa
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I don't have one to save HP. I have it to keep the engine between 175° and 185° on 100° days with the A-C running.
When the clutch on my old clutch fan let go, it tore up the shroud. I have also seen them tear up radiators.
I don't care if the electric costs 20HP, I wouldn't have another clutch fan on a bet. The smell of antifreeze under the car where ever I parked when running A-C was a constant reminder to keep an eye on the temp gauge. Now I seldom look at it, except to see if the engine is warm enough to turn on the heater on cold days - which is just like driving my new Equinox in that respect (which also has an electric fan).
another electric fan heard from.........
When the clutch on my old clutch fan let go, it tore up the shroud. I have also seen them tear up radiators.
I don't care if the electric costs 20HP, I wouldn't have another clutch fan on a bet. The smell of antifreeze under the car where ever I parked when running A-C was a constant reminder to keep an eye on the temp gauge. Now I seldom look at it, except to see if the engine is warm enough to turn on the heater on cold days - which is just like driving my new Equinox in that respect (which also has an electric fan).
another electric fan heard from.........
Last edited by magicv8; 10-09-2009 at 08:35 PM.
10-09-2009, 08:37 PM
#4
Le Mans Master
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I have an idea. Lets make this another overheating thread.....
I'll go first.
My car hasn't overheated since I installed my electric fan 5 years ago, and I haven't had to add a drop of antifreeze to the rad. That includes driving on Power Tours and in the mountains during summers with A-C.
5 years - that reminds me - it's time to change the HOAT.
PS: I will guess that the HP loss due to running 30° to 40° hotter than my 175° to 185° cost more HP than an electric fan uses. My car never had any torque in the city when the temp went to 220° and higher before I changed fans. On top of that the wiring insulation baked and the engine paint burned while cruise controls died in the underhood heat
I'll go first.
My car hasn't overheated since I installed my electric fan 5 years ago, and I haven't had to add a drop of antifreeze to the rad. That includes driving on Power Tours and in the mountains during summers with A-C.
5 years - that reminds me - it's time to change the HOAT.
PS: I will guess that the HP loss due to running 30° to 40° hotter than my 175° to 185° cost more HP than an electric fan uses. My car never had any torque in the city when the temp went to 220° and higher before I changed fans. On top of that the wiring insulation baked and the engine paint burned while cruise controls died in the underhood heat
Last edited by magicv8; 10-09-2009 at 08:48 PM.
10-09-2009, 09:11 PM
#6
Le Mans Master
Thread Starter
Even with an electric fan, you don't need to lose that power.
Before I installed a 1-wire alternator, I had a microswitch attached to the carb such that when the secondaries kicked, in the field windings kicked out disabling the alternator and letting it free-wheel. A switch under the dash would by-pass this carb switch so that the alternator would continue to work with the secondaries open (for street use).
This was not done in the interest of more power, but in saving "parts store" alternators that would continually go out on me when drag racing. But..., I did turn my best times when the alternator would disable. The battery can easily sustain the needed electrical power without an alternator for the 13-14 seconds.
Before I installed a 1-wire alternator, I had a microswitch attached to the carb such that when the secondaries kicked, in the field windings kicked out disabling the alternator and letting it free-wheel. A switch under the dash would by-pass this carb switch so that the alternator would continue to work with the secondaries open (for street use).
This was not done in the interest of more power, but in saving "parts store" alternators that would continually go out on me when drag racing. But..., I did turn my best times when the alternator would disable. The battery can easily sustain the needed electrical power without an alternator for the 13-14 seconds.
10-10-2009, 01:11 AM
#8
Race Director
I would suggest not to buy cheapo fan clutches that are made in China or not to get them at Pick-A-Part. 
13-14 seconds? You need more HP.
Doug
13-14 seconds? You need more HP.
Doug
10-10-2009, 01:33 AM
#9
Drifting
I am with Doug. I also use a quality clutch and fan. Never an overheating problem. The clutch slips upon rapid acceleration and cools with no problem.
HotRod mag. ran an article years ago and tested all types of fans and the best was the stock style fan/clutch type. HP/cooling.
!3-14 seconds, WTF, 10-11 seconds, be a man.
HotRod mag. ran an article years ago and tested all types of fans and the best was the stock style fan/clutch type. HP/cooling.
!3-14 seconds, WTF, 10-11 seconds, be a man.
Last edited by vetrod62; 10-10-2009 at 01:35 AM.
10-10-2009, 02:11 AM
#10
Le Mans Master
Thread Starter
Some of you are missing the point.
I personally run a 7-blade Hayden flex fan, not an electric fan. It was the Trak Auto lifetime warrentee alternators that kept going out, not a fan clutch. But even the ignition will draw off the alternator and cost power. Even with a fan clutch, you stand to gain hp if you can get the alternator freewheeling out of the circuit.
Even with no power accessories running, when the secondaries open and the alternator cuts out, I could watch the amp gauge drop below zero. So even just the ignition puts a demand on the alternator and costs some power. When I would shift, and let up on the throttle for a moment, I would see the gauge swing to the charge side and instantly drop again when reopening the throttle disconnecting the field.
I personally run a 7-blade Hayden flex fan, not an electric fan. It was the Trak Auto lifetime warrentee alternators that kept going out, not a fan clutch. But even the ignition will draw off the alternator and cost power. Even with a fan clutch, you stand to gain hp if you can get the alternator freewheeling out of the circuit.
Even with no power accessories running, when the secondaries open and the alternator cuts out, I could watch the amp gauge drop below zero. So even just the ignition puts a demand on the alternator and costs some power. When I would shift, and let up on the throttle for a moment, I would see the gauge swing to the charge side and instantly drop again when reopening the throttle disconnecting the field.
Last edited by toddalin; 10-10-2009 at 02:14 AM.
10-10-2009, 06:33 AM
#11
Race Director
In this month's Car Craft Magazine they run a dyno test on a modified SBC. To check the hp gain associated with changing belt and pulley ratios, they "load" the alternator with an electric fan (and it ain't all that big). The results...
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
Plus as speed of the car increases any fan, flex, clutch or e uses less power (put any fan in 40+mph and watch it spin with no power source, ever hear of wind farms?)
So, a good test is to 1/4 mile drag race test each type of fan and calculate power loss. I would expect the e fan to win, as it should be shut off.
.
what was the amp draw on the test?
my <6 amp fan would have a better time than a 50 amp fan even shut off, as it weighs less.(2.4#) There is a chance the car would hook up better with less weight on the nose, so track testing is a must, imo.
Last edited by Matt Gruber; 10-10-2009 at 06:39 AM.
10-10-2009, 06:34 AM
#12
Race Director
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St. Jude Donor '07
when i was running my Lincoln Mark VII electric fan i 'wore' the brushes out in a new 95 amp alternator within 6 months... i went back to my flex fan
Bill
Bill
10-10-2009, 10:49 AM
#13
In this month's Car Craft Magazine they run a dyno test on a modified SBC. To check the hp gain associated with changing belt and pulley ratios, they "load" the alternator with an electric fan (and it ain't all that big). The results...
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
Loading the alternator (i.e., just turning on the fan) cost 8 hp and 7 ft-lb.
I've got to get a copy of that article!This news will not be well received in the C3 camp..........
10-10-2009, 12:30 PM
#14
Drifting
Horsepower depletion is actually based on type of fan used. Direct fan without clutch approximately 8 HP above 4000 rpm. Clutch fan after engine is at operating temperature can vary between 3.5 & 4 HP loss.
Electric fan .3 to .5 HP loss. But then power steering has a deficit between 5 & 6 HP loss, Air compressor when activated 10 to 12 HP loss. So the fan horsepower loss is really irrelevant unless you are considering all accessories. Its really about total accessory loss that should be considered. Why not go electric water pump and save a whopping 11 to 14 HP?
But I'm content with no power steering, no power brakes, no air pump, no air compressor. Just a clutch fan and awesome power the factory provided under the hood! I leave the splitting of HP hairs to you guys.
rustylugnuts
Electric fan .3 to .5 HP loss. But then power steering has a deficit between 5 & 6 HP loss, Air compressor when activated 10 to 12 HP loss. So the fan horsepower loss is really irrelevant unless you are considering all accessories. Its really about total accessory loss that should be considered. Why not go electric water pump and save a whopping 11 to 14 HP?
But I'm content with no power steering, no power brakes, no air pump, no air compressor. Just a clutch fan and awesome power the factory provided under the hood! I leave the splitting of HP hairs to you guys.
rustylugnuts
10-10-2009, 12:37 PM
#15
Le Mans Master
I am with Doug. I also use a quality clutch and fan. Never an overheating problem. The clutch slips upon rapid acceleration and cools with no problem.
HotRod mag. ran an article years ago and tested all types of fans and the best was the stock style fan/clutch type. HP/cooling.
!3-14 seconds, WTF, 10-11 seconds, be a man.
HotRod mag. ran an article years ago and tested all types of fans and the best was the stock style fan/clutch type. HP/cooling.
!3-14 seconds, WTF, 10-11 seconds, be a man.
10-10-2009, 01:38 PM
#17
Le Mans Master
Thread Starter
No, not according to their dyno testing.
In the article the engine was on the dyno stand with the alternator just powering the fan (and maybe the ignition, but that was not noted). They simply turned on the fan to put load on the alternator and saw the 8 hp and 7 ft-lb drop on the engine dyno.
10-10-2009, 01:55 PM
#18
Melting Slicks
Don't have time now but maybe somebody else wants to come up with some guestimates, figuring in mechanical and conversion losses...
1 horsepower=746 watts
1 horsepower=746 watts
10-10-2009, 01:56 PM
#19
Melting Slicks
Don't have time now but maybe somebody else wants to come up with some guestimates, figuring in mechanical and conversion losses...
std conversion: 1 horsepower=746 watts
std conversion: 1 horsepower=746 watts
10-10-2009, 02:35 PM
#20
Race Director
PS: I will guess that the HP loss due to running 30° to 40° hotter than my 175° to 185° cost more HP than an electric fan uses. My car never had any torque in the city when the temp went to 220° and higher before I changed fans. On top of that the wiring insulation baked and the engine paint burned while cruise controls died in the underhood heat
Maximum fuel efficiency and HP are realized in a car that has an operating temp of 210-220F, due to less heat loss to cooling jacket.
The Nascar guys run 220F for a reason,and it isn't lack of cooling capacity.
Doug